The present invention relates to a hole gauge in which a pair of contact points are relatively drawn farther from or closer to each other, while guided by tapered surfaces which are movable together with a spindle, so that the inner diameter of a small hole can be measured.
There is a conventional hole gauge of this type, in which a pair of highly elastic support arms are attached at one end to the body cover and at the other end fitted with contact points having hemisperhical outer surfaces; and in which said contact points are adapted to be moved by tapered surfaces which are themselves axially movable together with a spindle, radially of said spindle.
In a hole gauge of this type, however, in which the support arms are flexible so that the distance between two hemispherical contact points may be variable, it is necessary to shake the whole gauge until the distance between the outer surface of the contact points, turning within a hole to be measured, becomes maximum, where the outer surfaces of the contact points can match the inner diameter of the hole.